1. Field of the Invention
The present invention relates to cook stoves employing radiant elements and more particularly to an electronic radiant cooktop control circuit.
2. Background Art
Radiant cooking elements have become relatively commonplace with cooktops being employed as part of free standing units, a part of stove/oven combinations, or built in to a cabinet base.
The most common way to control a radiant cooking element is to use a so-called infinite switch. The switch is an electro-mechanical device utilizing a bi-metallic element to control the on/off cycle of the heating element. The usual arrangement of the elements is cycled fully on for a period of time and then turned off for a second period of time. The duration of the cycles and the on/off times and the method employed will normally depend upon the thermal mass of the food being cooked so as to provide relatively even temperature.
Yet another technique includes controlling the temperature by utilizing a triac device to control the amount of the alternating current line power supplied to the cooking element. This is commonly referred to as "phase firing" and operates in the manner similar to that utilized for light dimmers. In this method, problems frequently are involved because it is very difficult to control the phase angle so that triac fires accurately. It has been discovered that in this situation triacs can also be fired falsely by external noise or hits on the AC line.
A background art search directed to the subject matter of this application and conducted in the U.S. Patent and Trademark Office disclosed the following U.S. Letters Patent:
______________________________________ 4,607,320 4,859,834 4,660,057 4,933,535 4,714,822 5,151,871 ______________________________________
Review of the above patents all appear to relate to pulse width modulation control of radiant heat elements failed to disclose techniques like that set forth in the present invention. It was particularly noted that none of the above related to cookers except for U.S. Pat. No. 4,714,822 which was granted to Braun et al for a cooker with means for automatically controlling the heating of a pan with food material. The arrangement taught therein operates as the result of a microprocessor providing the needed control. None of the above patents would appear to claim, teach or disclose a cook top controller employing pulse width modulation utilizing circuitry as taught by the present invention.